IQR Outlier Fences Calculator
Compute quartiles and flag observations outside Tukey-style interquartile fences.
Your result
MATHEnter your values and select calculate.
On this page How it works & practical examples
How to use the IQR Outlier Fences Calculator
The tool sorts observations and uses position (n−1)p with linear interpolation for quartiles. Values exactly on a fence are retained; only strictly outside values are flagged.
The calculation
Worked example
Using linear-interpolated quartiles, 1, 2, 3, 4, 5, 6 and 20 give Q1 = 2.5, Q3 = 5.5 and IQR = 3. At k = 1.5, only 20 lies beyond the fences.
Assumptions and limits
Quartile conventions differ between software. A flagged value is not automatically an error, and the calculator does not delete it or determine its cause.
Common questions
Which inputs should I use?
The tool sorts observations and uses position (n−1)p with linear interpolation for quartiles. Values exactly on a fence are retained; only strictly outside values are flagged.
What does the result exclude?
Quartile conventions differ between software. A flagged value is not automatically an error, and the calculator does not delete it or determine its cause.